Tính nhanh : -2. 17 + 72.31 - 36.2.28
Tính nhanh : –72. 17 + 72.31 – 36.2.28.
–72. 17 + 72.31 – 36.228
= –72. 17 + 72.31 – 36.2.114
= –72. 17 + 72.31 – 72.114
= 72(–17 + 31 – 114)
= 72. (–100)
= –7200.